Preheat the oven to 400°F. Line a sheet tray with parchment paper, set aside. In a large bowl mix together the egg, parmesan, breadcrumbs, garlic powder, onion powder, oregano, salt, and pepper until fully combined. Add in the ground beef and mix it in until combined, I like to do this by hand.
Portion the meatball mix into 8 equal portions, roll them between your hands to form meatballs. Place them on the lined sheet tray not touching. Bake for 15-20 minutes until golden brown on the outside and the internal temperature reaches 165°F. Place the sheet tray on the counter until ready to assemble the cups.
Place the oven on 375°F. Spray 8 sections of a muffin tin with cooking spray. Lay the crescent dough out on a clean work surface and cut it into 8 even pieces. Gently press the cut dough into the greased sections of the muffin tins. Make sure the corners of the dough overlap the tin.
Divide 1 cup of the mozzarella cheese into the bottom of each cup.
Place the marinara sauce in a small bowl. Dip the meatballs one by one into the marinara until coated. Press a meatball into the cups. Fold the crescent dough flaps over themselves up and over the meatball to form little cups. Top with the remaining cheese.
Bake for 12-15 minutes until golden brown. Take the cups out immediately and serve with a parsley garnish, optional. Serve with more marinara on the side for dipping.
Notes
Spaghetti sauce can be used in place of marinara, use your favorite.
Frozen meatballs should work, they just will not be as thick.
These can be frozen, see my tips above on how to do that.
Other cheeses can be used, see above for ideas.
You can use regular crescent rolls in place of the dough sheet, make sure that the perforations are sealed really well.